1. Field of the Invention
The present invention relates, in general, to vehicle seat adjusters.
2. Description of the Art
Power seat adjusters are a popular option on many automotive vehicles and are frequently offered as standard equipment on higher priced vehicles. Such power seat adjusters are primarily used on the driver's seat and, sometimes, on the front passenger seat of the vehicle to provide selective horizontal fore and aft and vertical movement of the seat as well as seat back recliner movement to accommodate occupants of different size and height as well as to provide a comfortable seating position to suit each occupant's preference.
Such power seat adjusters typically carry a seat support frame which supports the seat bottom and sometimes the seat back of a vehicle seat. The seat support frame is mounted on first and second, spaced track assemblies, each formed of an upper track which is connected to the seat support frame and which is slidably mounted on a lower track anchored to the vehicle floor. A drive mechanism typically includes a electric motor which bi-directionally rotates a pair of drive shafts extending outward from the motor to a gear assembly or box mounted on each upper track. In one arrangement, each gear box rotates a lead screw extending longitudinally below and carried by each upper track. A drive block is fixedly mounted to each lower track and threadingly receives the lead screw to cause reciprocal, horizontal movement of the upper track and the attached seat support frame relative to the lower track which is fixed to the vehicle upon selective energization of the drive motor and the drive shafts.
Similar drive mechanisms are provided for vertical (up and down) adjustment of the seat support frame and, in a seat adjuster having a seat recliner adjustment mechanism, for angularly adjusting the position of the seat back with respect to the seat bottom. The vertical drive mechanism may also include separate front and rear edge seat adjustment drive mechanisms for selectively tilting the front and rear edges of the seat bottom independent of each other as well as simultaneously to raise and lower the entire vehicle seat or, in some applications, only the seat bottom or cushion.
However, the rigid connection between the gears in the gear assembly, the drive motor output shaft, the drive shaft, the lead screw and the drive block frequently leads to problems during assembly and operation of a vehicle power seat adjuster. It is inevitable in the manufacture and assembly of a mechanical mechanism, such as a power seat adjuster, that poor dimensional conditions, such as concentricity, TIR, and linear discrepancies from nominal design dimensions, can and typically do occur. These dimensional conditions, without correction, can cause various problems in the operation of a power seat adjuster, such as poor breakaway from a stop position, slow operation of the power seat adjuster in extreme temperatures, excessive wear of the components of the power seat adjuster, uneven operation of the power seat adjuster, and the generation of unpleasant sounds or squeal during the operation of the power seat adjuster. One primary source of such objectionable noise or squeal is the rotation of the metal lead screw in the metal drive block.
To address certain of these problems, power seat adjusters have been devised in which the drive block is rotatably mounted in a aperture in the lower track for rotation about an axis extending longitudinally through the drive block and perpendicular to the lower track as shown in U.S. Pat. No. 5,467,957. Such rotation of the drive block is achieved by freely mounting the drive block in the aperture in the lower track without any additional fasteners, or by using a fastener with an enlarged head. In this latter structure, a cylindrical mounting collar or boss extends from the drive block through the aperture in the lower track and receives the fastener in an internal threaded bore. The mounting collar has a length than the thickness of the lower track to provide a small amount of vertical play between the drive block and the lower track to permit rotation of the drive block in the aperture in the lower track. Such rotatable drive blocks accommodate variations in end-to-end alignment of the lead screw and the lower track.
It is also known to provide other drive blocks or bearing blocks used in a power seat adjuster to connect the drive shaft to a lead screw and/or to connect the lead screw to a seat block recliner linkage with freedom of movement about two mutually exclusive axes. In this structure, the drive block or bearing block is provided with a pair of outwardly extending legs which ride in slots in a support bracket to enable rotation of the drive or bearing block about an axis extending through the legs. The side walls of the bracket carrying the slots is also formed slightly wider than the drive or bearing block to provide a small amount of lateral translation of the drive or bearing block in the bracket.
While the above-described vehicle seat adjuster drive blocks have proven effective in so far as providing self-alignment to overcome tolerance build up and misalignment conditions, it would still be desirable to provide a drive block for a vehicle seat adjuster which reduces the noise generated by rotation of the lead screw within the drive block. It would also be desirable to provide a drive block which can conform to all alignment positions of the lead screw relative to a lower track or other component of a vehicle seat adjuster. It would also be desirable to provide such a drive block which does not require major modification of the vehicle seat adjuster components.